Yes He was alive before the Law was written. He believed and it was accounted to Him for righteousness. So His religion was simple faith in God's promises. He entered into a covenant with God which was signified by circumcision.
Noah was given commandments relative to the building of the ark and the saving of his family. (Ge 6:22) After the Flood he was given laws that allowed the adding of flesh to man’s diet; declared the sacredness of life and therefore of blood, in which is the life; prohibited the eating of blood; condemned murder; and instituted capital punishment for this crime.—Ge 9:3-6.
The patriarch was a family head and ruler. Jehovah is designated as the great Family Head, or Patriarch, “the Father, to whom every family in heaven and on earth owes its name.” (Eph 3:14,*15) Noah, Abraham, Isaac, and Jacob are outstanding examples of patriarchs. These were especially dealt with by Jehovah. Abraham was given the command to circumcise all the males of his household as a sign of God’s covenant with him. (Ge 17:11,*12) He observed Jehovah’s “commands,” “statutes,” and “laws.” He knew Jehovah’s way to do righteousness and judgment and he laid these commands on his household.—Ge 26:4,*5; 18:19.